Project Summary/Abstract We have smartly formulated a large collection of novel TnCs to enhance or reduce cardiac muscle contractility in vivo. Using gene therapy approaches, we will test whether these engineered proteins can be used as novel therapies against a wide spectrum of acquired and inherited cardiac diseases. Specifically, we have developed a novel approach to enhance cardiac muscle contractility without compromising relaxation or making the heart an arrhythmic substrate. We have also engineered a novel approach to reduce hypercontractility of a diseased heart and enhance its relaxation. Furthermore, these studies will establish the potential of using engineered TnCs as a therapeutic tool to help patients suffering from several different cardiovascular diseases. We recently demonstrated that our smartly formulated L48Q TnC therapeutically increases in vivo cardiac contractility, function and performance after an MI. Our new exciting preliminary data demonstrates that cardiac contractility, function and performance can also be enhanced by L48Q TnC following a transverse aortic constriction (TAC; pressure overload on the left heart), without compromising relaxation/diastolic function. The purpose of this proposal is multifold and will: 1) demonstrate the broader therapeutic impact and clinical relevance of our smartly formulated TnCs on cardiovascular diseases with vastly different etiologies; 2) determine whether increasing contractility preserves cardiac function and performance of the right heart in pulmonary hypertension and the left heart in TAC; and 3) determine whether our smartly formulated TnCs can be used to combat inherited restrictive, hypertrophic and dilated cardiomyopathies. Aim 1. Determine if our smartly formulated TnCs can improve heart function in right and left sided he art failure . Pressure overload of the right and left heart are common and devastating diseases that compromise cardiac function and performance. Our battery of examinations will thoroughly test if cardiac muscle contractility can be tuned from the myocyte to in vivo by our novel engineered TnCs to combat left and right heart pressure overload. Aim 2. Determine if smartly formulated TnCs can improve heart function in inherited cardiomyopathies that model the human diseases. Inherited cardiomyopathies also compromise the contractility of the heart. We will test if smartly formulated TnCs can be used to combat these diverse cardiac diseases and improve the in vivo function and performance of the heart. The completion of this proposal will establish the potential of our novel translational strategies to help combat a broad range of cardiovascular diseases.